Preparation And Properties Of PS/Attapulgite, PU/Attapulgite And Their Composites

In recent years,polymer/clay nanocomposites have attracted a great deal of attention because addition of a low volume fraction of clay to polymeric matrix will significantly enhance the physical properties,such as mechanical and barrier properties,flammability resistance and thermal stability.Attapulgite(AT) is classified as a three-layer inverted mineral of fibrous habit with the theoretical half-unit-cell formula of[Mg₅Si₈O₂₀(OH₂)₄·4H₂O].It is characterized as a randomly oriented network of densely packed rods with the diameter of a single rod less than 100 nm and the length of a rod from several hundreds of nanometers to several micrometers.Polystyrene(PS) features good physical properties,such as easy to process and low cost with flaws as poor heat-resistance and easy to burn.And Polyurethanes(PU) are becoming increasingly important as engineering materials.Conventional PU, however,is known to exhibit poorer resistance to heat and lower mechanical properties.To overcome disadvantages of PS and PU,we prepared PS/AT,PU/AT and their composites via in-situ polymerization as following:1) Polystyrene(PS)/ Attapulgite(AT) composites were successfully prepared via in-situ Polymerization.TEM microphotographs showed that AT was irregularly dispersed in the PS matrix.The results of DSC and DMA showed that there existed interaction between the molecular chains of PS and AT,which led glass transition temperature of PS/AT composites shift to higher temperature.TGA illustrated that thermal resistance of PS/AT composites was improved with the addition of AT.The kinetics of thermal decomposition of PS/AT composites was described by Coats-Redfern equation and the activation energy of thermal decomposition was calculated,which increased with growing amount of AT.2) Polyurethane(PU)/Attapulgite(AT) composites were prepared by in-situ polymerization.SEM examination showed that AT particles were irregularly dispersed in the PU matrix in nanometer scales.DMA suggested that the storage modulus of PU/AT composites was increased and the glass transition temperature of soft segments shifted to higher temperature than the pristine PU.The mechanical properties of the composites,examined by tensile tests,showed higher tensile strength and elongation at break than that of the pristine PU.3) HPU/PS-IPNs copolymers were prepared by in-situ polymerization. 2-hydroxylethyl methacrylate(HEMA) terminated polyurethane(HPU) has been synthesized from poly(oxytetramethylene) glycol(PTMG),tolylene diisocyanate (TDI),and 2-hydroxylethyl methacrylate(HEMA).The HPU/PS-IPNs copolymers have been prepared from HPU and styrene under the initiation of AIBN.SEM examination showed that the network of HPU/St(50/50) was formed with best compatibility.The copolymers have cross-link network structures and two-phase morphology as determined by DMA.Strong interaction between HPU and PS phases has been observed,as indicated by the shift of Tg of the copolymers,which results from the cross-linking effect of PS and HPU molecular chains.The mechanical properties of the copolymers,examined by tensile tests,showed the tensile strength of HPU/St(10/90) was increased by 164%as compare to that of pure PS.4) AT/HPU/PS-IPNs composites were prepared by in-situ polymerization.SEM examination showed that AT particles were irregularly dispersed in the HPU/PS-IPNs matrix in nanometer scales.DMA suggested that the storage modulus of AT/HPU/PS-IPNs composites was increased and the glass transition temperature shifted to higher than the HPU/PS-IPNs matrix.The mechanical properties of the AT /HPU/PS-IPNs composites,examined by tensile tests,showed higher tensile strength and impact strength than that of the HPU/PS-IPNs matrix.